FIG. 1 depicts an air-bearing surface (ABS) view of a conventional read transducer used in magnetic recording technology applications. The conventional read transducer 10 includes shields 12 and 18, insulator 14, hard bias structures 16, and sensor 20. The read sensor 20 is typically a giant magnetoresistive (GMR) sensor or tunneling magnetoresistive (TMR) sensor. The read sensor 20 includes an antiferromagnetic (AFM) layer 22, a pinned layer 24, a nonmagnetic spacer layer 26, and a free layer 28. Also shown is a capping layer 30. In addition, seed layer(s) may be used. The free layer 28 has a magnetization sensitive to an external magnetic field. Thus, the free layer 28 functions as a sensor layer for the magnetoresistive sensor 20. Consequently, as used herein a sensor layer 28 is typically a free layer.
If the sensor 20 is to be used in a current perpendicular to plane (CPP) configuration, the insulator 14 is used. Thus, current is driven in a direction substantially perpendicular to the plane of the layers 22, 24, 26, and 28. Conversely, in a current parallel to plane (CIP) configuration, then conductive leads (not shown) would be provided on the hard bias structures 16.
The hard bias structures 16 are used to magnetically bias the sensor layer 28. In an ideal case, the hard bias structures 16 match the thickness, moment, and location of the sensor layer 28. The hard bias structures 16 typically include hard magnetic materials having a low permeability. The hard bias structures generally have a magnetization fixed in the working ranges of the transducer. The hard bias structures 16 typically magnetically bias the magnetization of the sensor layer 28 in the track width direction.
Although the conventional transducer 10 functions, there are drawbacks. The conventional transducer 10 has a shield-to-shield spacing of SS and a physical width of the sensor layer 28 of w. In general, the shield-to-shield spacing is desired to be reduced as higher density memories are to be read. Similarly, the track width is generally decreased as reading of higher density memories and thus higher cross-track resolution are desired. The cross-track resolution of the sensor layer 28 is primarily determined by the physical width, w, of the sensor layer 28. However, magnetic flux entering from the sides of the sensor layer 28 can adversely impact cross-track resolution. Stated differently, magnetic flux entering from the sides of the sensor layer 28 may influence the ability of the sensor layer 28 to accurately read data. The shields 12 and 18 may prevent some flux from reaching the sides of the sensor layer 28. However, as technologies scale to higher recording densities, the shield-to-shield spacing does not decrease sufficiently to address this issue. In addition, other recording mechanisms, such as shingle recording, may require improved cross-track resolution.
A conventional method for improving the cross-track resolution of the conventional transducer 10 is to introduce an in-stack hard bias layer in connection with side shields. An in-stack hard bias layer is one which resides between (on a line parallel to the down track direction) the sensor layer 28 and the shield 12 or directly between the sensor layer 28 and the shield 18. Generally, the in-stack hard bias would reside directly above (in the down track direction/toward shield 18) the sensor layer 28. The in-stack hard bias layer is desired to maintain the magnetic biasing of the sensor layer 28 in the track direction. Thus, the in-stack hard bias layer may replace the hard bias structures 16. However, such an in-stack hard bias layer would increase the shield-to-shield spacing, SS, of the transducer 10. Such an increase is undesirable.
Accordingly, what is needed is a system and method for improving the cross-track resolution of a magnetic recording read transducer.